1. Field of the Invention
This invention relates to an apparatus for controlling a machine for making bags or sacks, which are severed by hot-wire welding from tubular or semitubular webs of synthetic thermoplastics, which machine comprises a pair of web-feeding rollers, which are driven by a motor directly or via a transmission, a pair of welding jaws, which serve to form seam welds, transverse seam welds or hot-wire-welded transverse seams in the web and are operable by a second motor via a transmission, and which machine optionally comprises additional processing means which are provided with drive means and may consist, e.g., of punching means, perforating knives and/or receiving means or stacking means, said apparatus comprising a central processing unit for controlling the motors so that the motor for the pair of welding jaws is energized at a time at which the motor for driving the pair of feed rollers is still energized and after a standstill period of the motor for the pair of feed rollers that motor is already energized before the motor for the pair of welding jaws has stopped.
2. Description of the Prior Art
An apparatus of that kind is known from European Patent Publication 297 434. In the known apparatus the drive means for the feed rollers and for the welding jaws can be decoupled so that the output rate of the machine can be increased because the standstill times will be independent of the feeding times and can be restricted to the actual welding times and because the operating times of the motors overlap each other in part so that a maximum output rate can be obtained and unproductive times can be avoided.
It is not always desired to operate the machine at the highest possible output rate. It may be suitable to operate the machine at an output rate which has been reduced in adaptation to other production means or to certain production sequences.